After their period of use in the reactor, the spent fuel elements are extracted from the reactor and, before further processing, are first stored intermediately in a fuel element store. After the shutdown of the plant and the reduction in temperature, the impurities adhering to the surface of the cladding tubes of fuel elements, and designated in power station terminology as "crud", come loose. This stripping effect is intensified when the fuel elements are being transported under water from the reactor pressure vessel to the fuel element storage racks or from the fuel element storage racks to the transport containers. During unloading under water, the previously flooded container is lowered into the unloading part of the store which is designed as a water pool. After the transport containers have been opened, the 4-5 metre long fuel elements are extracted from the container with the aid of underwater gripping tools, are inserted into cans and are introduced into the storage racks by means of a crane. The water serves as a shield and at the same time ensures an excellent view during unloading manipulations. On the other hand, however, as mentioned, because of its flow movement it also at the same time assists the effect of stripping the crud from the fuel elements, with the result that the fuel element storage pool becomes contaminated.